Coherent structures in turbulent duct flow and control strategies of turbulence on wings

Abstract. Various control strategies are effective in reducing the skin-friction in canonical turbulent flows, such as channel flow and developing turbulent boundary layers. However, it is still unclear whether they can be applied to finite bodies to improve their overall aerodynamic properties. The first aim of this project is to characterize how three different control techniques, i.e. uniform blowing, uniform suction, and body-force damping, affect the flow around a NACA 4412 airfoil. A major source of difficulties in developing effective control techniques is the characteristic complexity of instantaneous turbulent flows. Therefore, the second aim of this project is to investigate whether three-dimensional coherent structures defined as connected regions of the physical domain are a useful tool to explain specific properties of such systems. The secondary flow in turbulent ducts is considered as a study case for coherent structure analysis.